ABSTRACT
The existence of a functional relationship between the thymus and the neuroendocrine system has been suggested by a number of observations dealing either with possible neurohormonal alterations following the removal of the thymus or with the modifications which may be induced within the thymus itself by different endocrine manipulations. This chapter demonstrates that the determination of some morphological and functional parameters of aging is clearly related to thymic involution. Central and autonomic nervous system, endocrine balance, and metabolic turnover have been shown to play a role in the development and maintenance of the immune system. A number of observations demonstrated that, although the thymus-dependent immunity has an highly sophisticated autoregulatory mechanism, much of its efficiency is influenced by extraimmunological homeostasis mechanisms. Thus, reduced thymic hormone content has been observed in hypophysectomized, thyroidectomized, and adrenalectomized rats, whereas increased amounts were recorded in castrated animals.
